It was known in the prior art to combine various oils and greases with powders of polymeric fluorocarbons in order to positively increase the lubricating quality and durability of the lubricant. U.S. Pat. No. 3,664,956 granted May 3, 1972 to Messina, et al, discloses a lubricant comprising polytetrafluoroethylene in combination with polysiloxanes and a grease composition.
Typically, these oil and grease based lubricants contained other additives in addition to polymeric fluorocarbons so as to create or improve a characteristic of the lubricating composition.
For instance, U.S. Pat. No. 4,224,173 granted Sept. 23, 1980 to Reick, discloses the use of a lubricating oil containing polytetrafluoroethylene (PTFE) particles and a fluorochemical surfactant for stabilizing the oil-PTFE dispersion and reducing volatilization losses during use of the lubricant in an internal combustion engine.
In U.S. Pat. No. 3,723,317 granted Mar. 27, 1973 to Ulery, lubricating greases are disclosed which comprise a fluorinated polyesther, a base oil, PTFE and a triazine compound for improving anti-corrosive and air oxidation resistance qualities of the lubricant.
The prior art in U.S. Pat. No. 3,933,656 granted Jan. 20, 1976 to Rick, also discloses a lubricant comprising a base oil intermixed with a dispersion of PTFE particles and a silane which, acting as a charge neutralizing compound, prevents a clumping together of the PTFE particles in suspension.
In order to enable the lubricant dispersions to retain their structural integrity and stability under extreme pressure and temperature and sheer stress conditions and to prevent the settling out of suspended particles such as PTFE, the prior art typically added thickeners such as fatty acid soaps, metal salts, mineral diatoms and organic polymers. U.S. Pat. No. 3,493,513 granted Feb. 3, 1970 to Petriello, discloses a lubricating grease and oil composition comprising a base oil, PTFE particles and a selected amount of polyethylene added as a thickener. U.S. Pat. No. 3,639,237 granted Feb. 1, 1971 to Curtis also relates to a lubricant grease which comprises a base oil, PTFE powder, and further comprises colloidal asbestos and other inorganic thickeners selected from talc, graphite and Group I, II and IV metal oxides and carbonates.
However, the grease compositions embodying these thickening agents typically fail in prolonged or excessive service or storage. Further, the metal salts in some bearing systems can be corrosive to the metallurgical entities and can cause stress cracking in plastic bearings. In addition, the mineral diatoms are frequently hygroscopic and can induce hydrolytic breakdown of the oil base and undergo bleed-out, a phenomena whereby the physical saturation or adsorption changes under bearing stress. Polyethylene while substantially resistant to hydrolytic reaction undergoes slow but relentless oxidation and crystallization under frictional wear and stress. In addition, grease containing asbestos fibers may be abrasive. Many of the thickeners used may also increase the toxicity of the lubricant within which it is used, thereby restricting its possible commercial applications.
Furthermore, many current grease-type lubricants are generally inoperable over a wide temperature range, especially at extremely low temperatures, and are thus not completely suitable for many potential commercial or military applications. For example, where lubricants do not possess physical characteristics which will permit their successful and reliable operation in equipment at extremely low temperatures, serious operational problems are introduced which often necessitates the use of auxiliary heaters to raise ambient temperatures.
It is therefore an object of this invention to provide improved lubricant compositions which are free of the abovementioned disadvantages.
It is a further object of this invention to provide an improved and uniquely different lubricant endowed with significantly greater endurance, wide service temperature range, good shear and oxidation stability and high electrical resistance, and a novel method for making the composition.
It is an additional object of this invention to provide a unique lubricant with a low toxicity and extended shelf life.
The aforesaid as well as other objects and advantages will be made more apparent in reading the following description and the adjoined claims.